Not common but not unheard of either.
This chimney breast leading to the chimney stack remains in the roof space. The chimney breast in the bedroom below it has been removed.
All the weight of the chimney is unsupported creating a potentially dangerous situation for structural instability (and the occupier).
The retained structure should either be completely removed or alternatively, and more sensibly/cheaply, supported from the underside with a reinforced concrete lintel, RSJ or similar.